1) I don't think there are any future plans to port the engine to a different platform.

2) The good thing about GameStudio is that you can add your own functionality. Generating a height map from a bitmap (at runtime) would just be about parsing pixels from a bitmap, and turning them into height coordinates. I don't really have experience with this so maybe someone else can help, lol.

3) There are a couple of tools floating about, eg Icex editor. I'm actually working on one at the moment.